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    <title>Document</title>
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    <script>
        /*      题目描述：把下面数组的首尾两个元素互换
             push  pop  shift  unshift
                 var arr = [1,2,3,4,5,6,7,8]； 
         互换之后: var arr = [8,7,6,5,4,3,2,1] */

        var arr = [1, 2, 3, 4, 5, 6, 7, 8];
          

        for(let i=0;i<4;i++){
          let tamp = arr[i];
          arr[i] =  arr[arr.length-1-i];
          arr[arr.length-1-i] = tamp;
        }
        console.log(arr);


    </script>
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